CA1289821C - Screw propeller boss cap with fins - Google Patents
Screw propeller boss cap with finsInfo
- Publication number
- CA1289821C CA1289821C CA 543348 CA543348A CA1289821C CA 1289821 C CA1289821 C CA 1289821C CA 543348 CA543348 CA 543348 CA 543348 A CA543348 A CA 543348A CA 1289821 C CA1289821 C CA 1289821C
- Authority
- CA
- Canada
- Prior art keywords
- propeller
- fins
- cap
- roots
- cap body
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63H—MARINE PROPULSION OR STEERING
- B63H1/00—Propulsive elements directly acting on water
- B63H1/02—Propulsive elements directly acting on water of rotary type
- B63H1/12—Propulsive elements directly acting on water of rotary type with rotation axis substantially in propulsive direction
- B63H1/14—Propellers
- B63H1/28—Other means for improving propeller efficiency
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63H—MARINE PROPULSION OR STEERING
- B63H1/00—Propulsive elements directly acting on water
- B63H1/02—Propulsive elements directly acting on water of rotary type
- B63H1/12—Propulsive elements directly acting on water of rotary type with rotation axis substantially in propulsive direction
- B63H1/14—Propellers
- B63H1/28—Other means for improving propeller efficiency
- B63H2001/283—Propeller hub caps with fins having a pitch different from pitch of propeller blades, or a helix hand opposed to the propellers' helix hand
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Mixers Of The Rotary Stirring Type (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A screw propeller boss cap with fins is provided to increase the propeller characteristics particularly the propeller efficiency. Owing to the fins on the boss cap, the water stream rearward of the boss cap is guided to a direction of reducing the generation of the hub vortex and on that score the propeller efficiency is increased. The fins should satisfy the conditions as follows:
(i) they are of the same number for each propeller blade, (ii) they have the inclination "Alpha" from -20° to +30° against the geometric pitch angle "Epsilon" of a propeller blade root, that is, -20° ? "Alpha" -"Epsilon" ? 30°, and the leading edge located between the adjacent propeller blade roots, and (iii) they have the maximum diameter larger than the diameter of the cap-mounting end of the boss and not larger than 33% of the propeller diameter.
Thus the propeller characteristics can be greatly improved by a rather simple and economically practicable means.
A screw propeller boss cap with fins is provided to increase the propeller characteristics particularly the propeller efficiency. Owing to the fins on the boss cap, the water stream rearward of the boss cap is guided to a direction of reducing the generation of the hub vortex and on that score the propeller efficiency is increased. The fins should satisfy the conditions as follows:
(i) they are of the same number for each propeller blade, (ii) they have the inclination "Alpha" from -20° to +30° against the geometric pitch angle "Epsilon" of a propeller blade root, that is, -20° ? "Alpha" -"Epsilon" ? 30°, and the leading edge located between the adjacent propeller blade roots, and (iii) they have the maximum diameter larger than the diameter of the cap-mounting end of the boss and not larger than 33% of the propeller diameter.
Thus the propeller characteristics can be greatly improved by a rather simple and economically practicable means.
Description
9~21 BACKGROUND OF THE INVENTION
Field of the invention . .
. The present invention relates to a boss cap of a screw propeller, particularly to a screw propeller boss cap - with fins.
. Description of the prior art . . .
In order to improve the characteristics of a screw propeller, particularly the propeller efficiency, extensive and intensive researches have already been made by engineers with respect to the technical design of number, shape, developed area, pitch, etc. of blades and now their fruits materially have been brought forth to a nearly maximum extent. Thus it is extremely difficult to expect any future drastic improvement of the propeller characteristics through researches on these items.
On the other hand, it has been known that the propeller efficiency of a screw propeller is low in the proximity of its boss. For this reason, it has been proposed for several times to provide a small diameter propeller at the rear stream side of the main propeller so that the propeller efficiency in the proximity of its boss .
, ~ ' ' ' - '' . . ~ ~ - .
'- ~
', ' may be raised, for example, in the Japanese Utility Model Laid-opens Nos. 30,195/81 and 139,500/82. It seems however that such idea in fact was not successful, probably for the reason that the thrust does not so much increase as the torque increases and thus the propeller efficiency is not so improved as expected.
SUMMA~Y OF THE INVENTION
.
An object of the present invention therefore is to provide a new technique which enables to improve the propeller characteristics particularly the propeller efficiency to a considerably high extent through addition of a boss cap with fins to a propeller.
As shown in the attached drawing of Eig. 3 (prior art technique), an ordinary screw propeller 31 comprises a plurality of blades 33 provided in a equidistance around the periphery of a boss 32 and is connected through the boss 32 to a rotational drive shaft 34. On an end opposite to the drive shaft 34 of the boss 32, a conical boss cap 35 is mounted in order to reduce vortices generated downstream of the boss 32 as much as possible.
The present inventors have focused their attention on the fact that even in the rear stream of such propeller .. . . .
~ ' , - ~ - .
1~982~
71g93-2 boss cap, a considerable hub vortex 36 is generated and, in the thought that the prior a~t small diameter additional propeller would have increased such hub YOrteX, have made intensive researches seeking to find any other means for reducinq such hub vortex. Finally it has been found tha~ the addition of a boss cap with fins to a propeller can reduce such hub vor~ex and in effect can increase the propeller efficiency.
Thus the present invention provides in combination: a screw propeller having a hub and a plurality of propeller blades thereon each havlng a leading edge toward a front of the propeller and a tralllng edge toward the rear of the propeller and a root along a root line on the hub extending from the leading edge to the trailing edge, said roots lying along a line at a pitch angle to a plane perpendicular to the axis of rotation of said propeller; and a cap body having a front cap mounting end mounted on said hub at the rear of said propeller, and a rear end, a plurality of fins mounted on said cap body at intervals spaced around the periphery of said cap body, (1) the number o~ fins belng the same as the number of propeller blades and respectively corresponding to the propeller blades, (ii) sald fins being inclined at an angle to the line along which the root of the corresponding propeller blade lies, which angle is from -20 to +30 relative to the rotational direction of the screw propeller and is selected to receive`a stream from the propeller blades at a side facing toward the propeller blades, and being inclined at a rake angle RA which is -30 ~ RA c 0 relative to the direction of rotation of said screw propeller, and said fins having leading ~.
edges which are toward said propeller and which are behind the rear end of the roots of said propeller blades and between lines starting respectively from the leading and trailing edges of the roots of the propeller blades and extending rearwardly in parallel to the axis of rotation of said propeller, said fins being substantially smaller in blade area than the propeller blades and having roots along said cap body, the ends of the roots of trailing edges of said fins spaced in the circumferential direction of said cap body and being spaced toward said propeller from the rear end of said cap body; and (iii) the outer diametric dimension of said fins from the axis of said cap being larger than the diameter of said cap body at the rear of said propeller hub and no larger than 33% of the outer diametric dimension of said screw propeller as measured from the axis of rotation of the screw propeller.
4a <~
,:~
:, :' ., : ~ . , ~ . ' ~ . : -, ~' , ' -' .
l~9~Xl The fins provided according to the present invention are not those for generating a thrust by themselves, hut for guiding the water stream rearward of the boss cap to a direction to reduce the generation of the hub vortex.
Owing to such guide effect, the hub vortex in the rearward of the boss cap is diffused and thus the drag force induced by the vortex on a propeller blade plane is reduced and as the result the propeller characteristics particularly the propeller efficiency are greatly improved without remarkable increase of the torque.
Accordingly, as a general tendency, the present invention gives a particularly higher effect to a propeller having a higher pitch ratio ~H/D) which generates a stronger hub vortex.
As shown in the embodiments of the present invention hereinafter, the fins may be provided to have a rake angle or a positive or negative camber against the boss cap.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a front view of a propeller on which an ..
embodiment of the propeller boss cap with fins of the present invention is mounted, and Fig. 2 is a side view of the Fig. 1.
Fig. 3 is a side view similar to the Fig. 2, but shows a propeller and a boss cap of prior art technique without fins together with a hub vortex generated rearward of the boss cap.
Fig. 4 is a side view partly shown in the section of a propeller characteristics measurement apparatus used in the experiments.
Fig. 5 is a plan view showing plane shape of the fins used in the experiments and Fig. 6 is a side view showing the mounting positions of the fins to the propeller boss cap.
Fig. 7 shows the propeller characteristics curves obtained in the Experiment No. 1 and Figs. 8-10 show the schematic illustrations representative of the relative positions of the propeller blades roots and the fins in the Experiments Nos. 2-4, respectively.
Fig. 11 is a side view to show the rake angle of the fins in the Experiment No. S and Fig. 12 is an A-A line , 12~2~ .
sectional view of the Fig. 11.
Fig. 13 is a schematic illustration similar to the Figs. 8-10, but showing the relative positions of the propeller blades roots and the fins in the Experiment No. 6.
Fig. 14 is a diagram showing the results of the Experiment No. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Some embodiments of the present invention will be explained in detail with reference to the attached drawings.
Tests are made in a water tank, using models of propellers having the data as shown in the following table 1. The water tank is of a circular stream type and has an observational part of scales 5.0 m (length) X 2.0 m (width) X
1.0 m (depth). The maximum flow rate is 2.0 m/sec and the uniformity of the flow rate is within 1.5~.
Table 1 Type CP24 CP26 Diameter (mm) 220.0 220.0 Pitch ratio 0.8 1.2 ~2~9821 Developed ~lade area ratio 0.55 0.55 Boss ratio 0.18 0.18 Blade thikness ratio 0.05 0.05 Blade cross section shape MAU MAU
Blade number 4 4 In Fig. 4, a side view of a propeller characteristics measurement apparatus is shown partly by a section. This apparatus is located in the observational part of said water tank by securing its propeller open boat 41 to a rigid carrier (not shown) placed above the water tank. The boat 41 has a drive mechanism 43 to rotate a propeller 42 which may detachably be attached to its tip end, a thrust detector 44 and a torque detector 45.
Although not shown in the Fig. 4, a propeller rotating speed i5 measured by a digital counter TM-225 (product of Ono Measurement Instruments company, Japan) and a flow rate by a combination of a JIS type Pitot tube and a differential pressure converter DLPU-0.02 (product of Toyo Boldwin company, Japan). The analogue signals of such thrust, torque and flow rate represented by the differential pressure, etc. are converted to digital signals through an A/D converter provided in a microprocessor located in a separate controller and processed into physical data which then are printed by a pinter or plotted by a plotter.
~' -; .
-~X~98~
A thrust coefficient (KT) and a torque coefficient(KQ) are measured under different advance coefficients (J) adjusted by changing the flow rate while keeping the propeller rotating speed approprimately constant within the range of 7.5-9.0 r.p.s.. The depth in water of the propeller center is 300 mm and the direction of water flow is as shown by an arrow in the Fig. 4.
As a boss cap to be mounted on the propeller models, a cap of a rounded conical shape having a base diameter of 35 mm and a height of 25.6 mm is prepared. The cap may be mounted on the propeller by any known means and in these experiments a bolt-nut securing is employed.
As fins to be provided on the boss cap, those having six different triangular shapes (A)-~F) shown by a plan view in Fig. 5 are prepared from flat plates of l mm thickness to have the dimensions as shown in the following table 2.
Table 2 Fin shape Width Height (X-axis direction) (Y-axis direction) . _ _ _ . .
(A) 20 mm 20 mm (B) 26 mm 16.5 mm 1~9~1 (C) 26 mm 21 mm (D) 26 mm 28.5 mm (E) 26 mm 34 mm (F) 26 mm 39.5 mm Fig. 6 shows the relative positions of the fins and the boss cap. In this Eig. 6, a rear end O of a root 62 of a propeller blade 61 is set on the propeller axis 63 as a reference point. In this specification, a peripheral distance from the front end of a fin 64 to the plane including the reference point O and the propeller axis 63 is called "a" (positive in the direction of propeller rotation shown by an arrow). A surface distance from the front end of the fin 64 to a periphery including the reference point O
is called "b". The angle of the fin 64 against plane normal to the propeller axis is called "Alpha". The geometric pitch angle of the propeller blade root 62 is called "Epsilon".
In this specification, the geometric pitch angle "Epsilon" of a propeller blade root is one based upon a nose-tail line of the propeller blade root. More precisely, two surfaces of a cylindrical surface having an axis on the propeller axis and a radius equal to the boss radius and a propeller blade surface or its extension as a suspected surface are considered. A cylindrical surface intercepted , . . ' , ~X~
by a crossing line between these two surfaces, that is, a cylindrical section, is developed on a plane. In the developed vlew, an angle between a nose-tail line of the blade section defined by the developed cylindrical section and a line normal to a generatrix of the cylindrical surface corresponds to the "Epsilon".
The fin 64 is mounted on the boss cap in the direction perpendicular to the sheet of the Fig. 6, when no rake angle is given. The mounting is made, in these experiments, by cutting a groove on the boss cap, inserting the lower portion of the fin into the groove and fixing by means of an adhesive, but it is of course possible and in actual cases it is preferred to form the boss cap and the fins integrally as one body. The broken lines shown in the lower portions of fins in the Fig. 5 indicate crossing lines between the fin surface and the boss cap surface after mounting of the former on the latter.
Experiment 1 Water tank tests have been made by using the propeller of the type CP26 (Epsilon=67.4) and the fins of Fig. 5(C). The fins of total number 4, one for each ::
. ' :
12~9~21 propeller blade, are mounted on the boss cap in positions of a=lO mm, b=5 mm and Alpha=66. In this instance, the maximum diameter of the fins, that is, a doubled distance (2r) between the radially remotest end of a fin (from the propeller axis) and the propeller axis (after mounting of the fins on the boss cap) and a propeller diameter (2R) stand in a ratio r/R=0.23. Fig. l shows a front view of thus composed propeller l, boss 2, propeller blades 3, shaft 4, boss cap 5 and fins 6; and Fig. 2 shows a side view thereof. For comparison, tests have been made also as to cases without fins. The thrust coefficient (KT) and the torque coefficient (KQ) have been measured under various advance coefficients (J) of 0.0-l.l and the propeller efficiency (Eta= J KT/2PiKQ) has been calculated. Then an increase ratio (dEta) of the propeller efficiency increased from the cases without fins to the cases with fins has been calculated by percents. The results are shown in the following tables 3 and 4.
'; ' ~ ' ~ ' , 1~9~
Table 3 ( cases without f ins ) No . J KT KQ x 10 Eta _ 0 0.000 0.4816 0.9376 0.0000 1 0.050 0.4715 0.9092 0.0413 2 0.100 0.4606 0.8823 0.0831 3 0.150 0.4489 0.8565 0.1251 4 0.200 0.4363 0.8316 0.1670 0.250 0.4230 0.8071 0.2085 6 0.300 0.4088 0.7829 0.2493 7 0.350 0.3940 0.7586 0.2893 8 0.400 0.3785 0.7342 0.3282 9 0.450 0.3623 0.7094 0.3657 0.500 0.3454 0.6839 0.4019 11 0.550 0.3281 0.6578 0.4365 12 0.600 0.3102 0.6309 0.4695 13 0.650 0.2919 0.6031 0.5007 14 0.700 0.2731 0.5743 0.5299 0.750 0.2541 0.54450.5571 16 0.800 0.2349 0.51380.5820 17 0.850 0.2154 0.48200.6046 18 0.900 0.1959 0.44940.6244 19 0.950 0.1764 0.41590.6413 1.000 0.1570 0.38170.6547 21 1.050 0.1378 0.34680.6639 22 1.100 0.1189 0.31150.6680 :, ': ' .
12~
Table 4 ( cases with ~ins ) .
No . J KT RQ x 10 Eta dEta ( % ) . _ . .
00.000 0.4985 0.9154 0.0000 10.050 0.4894 0.8914 0.0437 5.55 20.100 0.4785 0.8677 0.0878 5.35 30.150 0.4660 0.8440 0.1318 5.09 40.200 0.4522 0.8204 0.1755 4.81 50.250 0.4373 0.7965 0.2184 4.54 60.300 0.4215 0.7724 0.2605 4.29 70 350 0.4050 0.7479 ~.3016 4.09 80.400 0.3880 0.7~29 0.3417 3.96 90.450 0.3705 0.6973 0.3806 3.90 100.500 0.3528 0.6710 0.4184 3.95 110.550 0.3349 0.6441 0.4552 4.09 120.600 0.3168 0.6164 0.4909 4.35 130.650 0.2986 0.5879 0.5255 4.73 14 0.700 0.2803 0.5585 0.5590 5.21 0.750 0.2617 0.5284 0.5913 5.78 16 0.800 0.2430 0.4974 0.6220 6.42 17 0.850 0.2239 0.4655 0.6506 7.07 18 0.900 0.2044 0 ~ 4328 0.6762 7.66 19 0.950 0.1843 0.3994 0.6976 8.07 1.000 0.1634 0.3652 0.71~3 8.09 21 1.050 0.1417 0.3303 0.7168 7.38 22 1.100 0.1187 0.2947 0.7053 5.29 , '~`~,' '' :
' ' ' ,: .' . -Fig. 7 illustrates the results of the tables 3 and 4 showing the advance coefficient (J) in abscissa and the thrust coefficient (KT), the torque coefficient multiplied by ten (KQ x 10) and the propeller efficiency (Eta) in ordinate. In this Fig. 7, curves T2, Q2 and P2 represents KT, KQ x 10 and Eta in the table 3 and curves T3, Q3 and P3 represents KT, KQ x 10 and Eta in the table 4. From this Fig. 7 and the table 4, it is understood that the propeller efficiency increases about 4-8% in the overall range of J=0.05-1.10 and particularly 7.66% at the usually employed J=0.9.
Further, in these tests, a needle pipe is manually put into the water from above the water tank to the close proximity of the rear end of the boss cap to supply air bubbles. It has been found that in the cases without fins, a large number of air bubbles align along the propeller axis, but in the cases with fins, air bubbles are diffused to disappear. It is considered that a hub vortex is greatly reduced by the merit of the fins.
Experiment 2 Tests similar to those shown in the Experiment 1 have been made, but using different positions of fins, that is, different a, b and Alpha. The propeller efficiency ' . ~ . .
.
'"
~2~9~21 increase ratio obtained under the usually employed advance coefficient (J)=0.9 is shown in the following table 5.
Table 5 No. a b Alpha Alpha- r/R dEta (mm) (mm)(~) Epsilon() (~) .. , . . . -- -- :
1 10 0 64 -3.4 0.25 5.49 2 15 0 61 -6.4 0.25 7.32 3* 10 5 66 -1.4 0.23 7.66 4 14 5 59 -8.4 0.23 6.39 * . . . from the data in the Experiment 1 The relative positions of fins and the propeller blade roots are illustrated in Fig. 8, wherein the rear end O of one propeller blade root shown in the Fig. 6 is placed on the base line X, and the blade position is shown as a line segment starting from the base line X with an angle Epsilon and ha~ing a length corresponding to the length of the nose-tail line of the propeller blade root. Another propeller blade root adjacent to said one also is shown is a similar manner, but at a peripheral distance between the rear ends of them taken in the direction of the base line X.
The positions of the fins are shown by taking "a" of the Fig. 6 in the direction of the base line X and "b" of the . ~ i , . : . . -- .
.
- - : - ' ' : -.
-Fig. 6 in the direction of a base line Y which passesthrough the reference point O normally to the base line X.
The lengths of the fin segments correspond to the lengths of the crossing lines between the fins and the boss cap as shown in the Fig. 5 by broken lines. From the table 5 and the Fig. 8, it is understood that a considerable improvement of propeller efficiency can be obtained when the front ends of fins are placed between the adjacent propeller blade roots, that is, within a space between extended nose-tail lines of the adjacent propeller blade roots.
Experiment 3 Tests similar to those of Experiment 1 have been made, but changing on]y Alpha. The propeller efficiency increase ratio obtained at the advance coefficient (J)=0.9 is shown in the following table 6.
Table 6 No. Alpha~) Alpha-Epsilon() r/R dEta(%) 1 45 -22.4 0.24 0.34 2 S0 -17.4 0.235 3.46 3* 66 - 1.4 0.23 7.66 4 85 17.6 0.22 3.80 S 90 22.6 O.Z2 2.19 , - . - : ' :
: ~ ' '' ' ' .
' ., ~ ' - ~
~9~
- 18 - , 6 95 27.6 0.22 2.38 7 100 32.6 0.22 0.77 8 105 37.6 0.22 0.47 * . ~ . from the data of Experiment 1 The results of the table 6 are shown in Fig. 9 similarly to the Experiment 2. It is understood from the table 6 and the Fig. 9 that a considerable improvement of propeller efficiency can be obtained within the range of -20 c Alpha-Epsilon ~30 -Experiment 4 Tests similar to those of Experiment 2 have beenmade, but using the propeller of the type CP24 (Epsilon=57.4~) and the fins of the Fig. 5(A) and 5(C). The propeller efficiency increase ratio obtained at the advance coefficient (J)=0.6 usually employed for such propeller is shown in the following table 7.
Table 7 No. a b Alpha Alpha- r/R Fin shape dEta (mm) (mm) () Epsilon(~) (%) .. _ . _ . _ _ .
1 0 5 80 22.6 0.21 (A) 2.03 '''~
.. .. .
. . .
.. . . . .
' ' -' : . . ' .,:, ~ .:' ' , .- - . ~ i 2 10 17 63 5.6 0.18 (A) 3.02 3 5 12 63 5.6 0.20 (A) 2.06 4 5 9.5 63 5.6 0.21 (A) 2.32 7 63 5.6 0.215 (A) 2.84 6 10 7 63 5.6 0.23 (C) 3.93 7 10 7 57 -0.4 0.22 (C) 2.32 8 6 7 63 5.6 0.22 (C) 2.57 9 4 5 35-22.4 0.235 (C) -0.09 10 4 5 9032.6 0.22 (C) -O.lg The results of the table 7 are shown in Fig. 10 similarly to Experiment 2. It is understood that there is no material difference between the fin shapes (A) and (C) and that the fin positions should satisfy the conditions that the front end of the fin is located between the adjacent propeller blade roots and the inclination of the fin stands within the range of -20~Alpha-Epsilon S 30 , as in the case of said Fig. 9.
Ex ~
The test of Experiment 4, No. 6 has been repeated, adding rake angles of +30 to the fins~ The rake angles are measured from the direction perpendicular to the sheet of the Fig. 6 to the direction of rotation of the propeller.
The results are shown in the following table 8.
' ' ~ .
; , .
1~9~2~.
Table 8 No. a b Alpha Alpha- r/R Rake Angle dEta (mm) (mm) () Epsilon() () (~) 6F 10 7 63 5.6 0.21+30 1.46 6M* 10 7 63 5.6 0.23 0 3.93 6B 10 7 63 5.6 0.21-30 4.47 * . . . from the data of Experiment 4 From the table 8, it is understood that there is a tendency of further improvement of dEta when a rake angle opposite to the rotation direction of the propeller is added to fins. The mounting positions of fins are shown in Fig. 11 by way of a side view similar to the Fig. 6 and in Fig. 12 which is an A-A line section of the Fig. 11.
Experiment 6 The tests of Experiment 4, No. 7 has been repeated, but by changing the number and positions of the fins. the results are shown in the following table 9.
'~
' ' ' ~ ~ ',~ ',; ' ' ', : . . ~ - , -' . ', ~
: . , 12~
- Table 9 No.a b Alpha Alpha- r/R FindEta (mm) (mm) (o) Epsilon() Number (%?
7~N210** 7 57 -0.4 0.22 2-0.12 7-N310** 7 57 -0.4 0.22 30.49 7-N4* 10 7 57 -0.4 0.22 42.32 7-NS10** 7 57 -0.4 0.22 5-1.12 * . . . from the data of Experiment 4 ** . . . value of one specific fin; values of the other fins correspond to the positions determined by the quotient of 360 . divided by the number of f ins The relative positions of the propeller blade roots and the fins are shown in Fig. 13 by way of X-Y plane as in the Figs. 8-10. Relative to the four propeller blade roots Bl-B4, the fins are located, in the case of fin number two, at the positions l/F and 2/2; in the case of fin number three, at the positions l/F, 2/3 and 3/3; in the case of fin :. number four, at the positions l/F, 2/4, 3/4 and 4/4; and in : the case of fin number five, at the positions l/F, 2/5, 3/5, 4/5 and 5/5, as shown in the Fig. 13. It can be seen therefrom that there is no fin located, in the case of fin number two, between the propeller blade roots B2 and B3 and ;l .
-.
' 9~
between B4 anu Bl; in the case of fin number three, between s3 and s4. Further, there are two fins between B3 and B4 in the case of fin number five. Thus the fins are not evenly positioned in the cases of fin number two, three and five.
It is understood from the table 8 that the number of fins should be same for each space between the adjacent propeller blade roots.
Experiment 7 .
Tests similar to those of Experiment 1 have been made, but by using various fins of the Fig. 5(B)-5(F) having the same width but different heights. Total four same shape ; fins, one for each propeller blade, are mounted in the positions determined by a=10 mm, b=5 mm and Alpha=66. The propeller efficiency increase ratio obtained at the advance coefficient (J)=0.9 is shown in the following table 10.
Table 10 No. a b Alpha Alpha- r/R Fin shape dEta (mm) (mm) () Epsilont) (~) 1 10 5 66 -1.4 0.2 (B) 4.12 2* 10 5 66 -1.4 0.23 (C) 7.66 3 10 5 66 -1.4 0.3 (D) 6.08 ,:`,.`,`
.
., ' ': ' .: ~- - , 4 10 S 66 -1.4 0.35 (E) 0.87 5 66 ~1.4 0.4 (F) -0 50 * . . . from the data of Experiment 1 The results of the table 10 are illustrated in Fig. 14, taking r/R in abscissa and dEta in ordinate.
In view of the fact that the boss ratio of the propeller of type CP26 is 0.18, it is unerstood that the maximum diameter of the fins should be greater than the diameter of the cap-mounting end of the boss and not be greater than 33% of the propeller diameter, in order to obtain a considerable improvement of the propeller efficiency.
Experiment 8 Tests similar to those of Experiment 1 have been made, but by using fins of the Fig. 5(C) bended to an arc of radius 50 mm. Two kinds of fins, one bended to the arc convex in the direction of propeller rotation (= C-out) and the other to the arc concave in the direction of propeller rotation (= C-in), are used. Total four same shape fins, one for each propeller blade, are mounted in the positions dete_mined by a=10 mm, b=5 mm and Alpha=66~ (= angle of the ', ':
- ; : .
' ,- ' : . - ' .:
. , ~ .
~z~
direction of the chord of the arc). The propeller efficiency increase ratio as obtained at the advance coefficient (J)=0.9 is shown in the following table 11.
Table 11 No. a b Alpha Alpha- r/R Fin shape dEta (mm) (mm) () Epsilon() (%) _ 1 10 5 66 -1.4 0.23 C-out 6.46 2* 10 5 56 -1.4 0.23 C 7.66 3 10 5 66 -1.4 0.23 C-in 6.94 * . . . from the data of Experiment 1 From the above data, it is understood that the shape of fins is not limited to plane and may have a positive or a negative camber.
As explained in detail above, it is possible to improve the propeller characteristics particularly the propeller efficiency without increasing torque, by the effect of guiding the water stream rearward of the boss cap to a direction of reducing generation of hub vortex, through the provision of fins on a boss cap to be mounted on a screw propeller in accordance with the present invention.
, ' " ' ' ' ' ' . ' , ' ', ' ' , ~ , '' . ~ ' ' . ~ ' ' '" . . , ' ' ' . :
' . . .
.
' , ' .
According to such invention, further merits are obtained, for example, the propeller characteristics may greatly be improved only by a slight modification of a rather small boss cap and not by a drastic change of the screw propeller itself, to which the boss cap is appended, necessitating difficult work and high cost. In effect, the present invention is applicable to screw propellers already mounted on existing ships, simply by exchanging or working the boss cap without incurring high cost.
~ , .. ~ -, . , -.
- . .
., ' : ' ' :
Field of the invention . .
. The present invention relates to a boss cap of a screw propeller, particularly to a screw propeller boss cap - with fins.
. Description of the prior art . . .
In order to improve the characteristics of a screw propeller, particularly the propeller efficiency, extensive and intensive researches have already been made by engineers with respect to the technical design of number, shape, developed area, pitch, etc. of blades and now their fruits materially have been brought forth to a nearly maximum extent. Thus it is extremely difficult to expect any future drastic improvement of the propeller characteristics through researches on these items.
On the other hand, it has been known that the propeller efficiency of a screw propeller is low in the proximity of its boss. For this reason, it has been proposed for several times to provide a small diameter propeller at the rear stream side of the main propeller so that the propeller efficiency in the proximity of its boss .
, ~ ' ' ' - '' . . ~ ~ - .
'- ~
', ' may be raised, for example, in the Japanese Utility Model Laid-opens Nos. 30,195/81 and 139,500/82. It seems however that such idea in fact was not successful, probably for the reason that the thrust does not so much increase as the torque increases and thus the propeller efficiency is not so improved as expected.
SUMMA~Y OF THE INVENTION
.
An object of the present invention therefore is to provide a new technique which enables to improve the propeller characteristics particularly the propeller efficiency to a considerably high extent through addition of a boss cap with fins to a propeller.
As shown in the attached drawing of Eig. 3 (prior art technique), an ordinary screw propeller 31 comprises a plurality of blades 33 provided in a equidistance around the periphery of a boss 32 and is connected through the boss 32 to a rotational drive shaft 34. On an end opposite to the drive shaft 34 of the boss 32, a conical boss cap 35 is mounted in order to reduce vortices generated downstream of the boss 32 as much as possible.
The present inventors have focused their attention on the fact that even in the rear stream of such propeller .. . . .
~ ' , - ~ - .
1~982~
71g93-2 boss cap, a considerable hub vortex 36 is generated and, in the thought that the prior a~t small diameter additional propeller would have increased such hub YOrteX, have made intensive researches seeking to find any other means for reducinq such hub vortex. Finally it has been found tha~ the addition of a boss cap with fins to a propeller can reduce such hub vor~ex and in effect can increase the propeller efficiency.
Thus the present invention provides in combination: a screw propeller having a hub and a plurality of propeller blades thereon each havlng a leading edge toward a front of the propeller and a tralllng edge toward the rear of the propeller and a root along a root line on the hub extending from the leading edge to the trailing edge, said roots lying along a line at a pitch angle to a plane perpendicular to the axis of rotation of said propeller; and a cap body having a front cap mounting end mounted on said hub at the rear of said propeller, and a rear end, a plurality of fins mounted on said cap body at intervals spaced around the periphery of said cap body, (1) the number o~ fins belng the same as the number of propeller blades and respectively corresponding to the propeller blades, (ii) sald fins being inclined at an angle to the line along which the root of the corresponding propeller blade lies, which angle is from -20 to +30 relative to the rotational direction of the screw propeller and is selected to receive`a stream from the propeller blades at a side facing toward the propeller blades, and being inclined at a rake angle RA which is -30 ~ RA c 0 relative to the direction of rotation of said screw propeller, and said fins having leading ~.
edges which are toward said propeller and which are behind the rear end of the roots of said propeller blades and between lines starting respectively from the leading and trailing edges of the roots of the propeller blades and extending rearwardly in parallel to the axis of rotation of said propeller, said fins being substantially smaller in blade area than the propeller blades and having roots along said cap body, the ends of the roots of trailing edges of said fins spaced in the circumferential direction of said cap body and being spaced toward said propeller from the rear end of said cap body; and (iii) the outer diametric dimension of said fins from the axis of said cap being larger than the diameter of said cap body at the rear of said propeller hub and no larger than 33% of the outer diametric dimension of said screw propeller as measured from the axis of rotation of the screw propeller.
4a <~
,:~
:, :' ., : ~ . , ~ . ' ~ . : -, ~' , ' -' .
l~9~Xl The fins provided according to the present invention are not those for generating a thrust by themselves, hut for guiding the water stream rearward of the boss cap to a direction to reduce the generation of the hub vortex.
Owing to such guide effect, the hub vortex in the rearward of the boss cap is diffused and thus the drag force induced by the vortex on a propeller blade plane is reduced and as the result the propeller characteristics particularly the propeller efficiency are greatly improved without remarkable increase of the torque.
Accordingly, as a general tendency, the present invention gives a particularly higher effect to a propeller having a higher pitch ratio ~H/D) which generates a stronger hub vortex.
As shown in the embodiments of the present invention hereinafter, the fins may be provided to have a rake angle or a positive or negative camber against the boss cap.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a front view of a propeller on which an ..
embodiment of the propeller boss cap with fins of the present invention is mounted, and Fig. 2 is a side view of the Fig. 1.
Fig. 3 is a side view similar to the Fig. 2, but shows a propeller and a boss cap of prior art technique without fins together with a hub vortex generated rearward of the boss cap.
Fig. 4 is a side view partly shown in the section of a propeller characteristics measurement apparatus used in the experiments.
Fig. 5 is a plan view showing plane shape of the fins used in the experiments and Fig. 6 is a side view showing the mounting positions of the fins to the propeller boss cap.
Fig. 7 shows the propeller characteristics curves obtained in the Experiment No. 1 and Figs. 8-10 show the schematic illustrations representative of the relative positions of the propeller blades roots and the fins in the Experiments Nos. 2-4, respectively.
Fig. 11 is a side view to show the rake angle of the fins in the Experiment No. S and Fig. 12 is an A-A line , 12~2~ .
sectional view of the Fig. 11.
Fig. 13 is a schematic illustration similar to the Figs. 8-10, but showing the relative positions of the propeller blades roots and the fins in the Experiment No. 6.
Fig. 14 is a diagram showing the results of the Experiment No. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Some embodiments of the present invention will be explained in detail with reference to the attached drawings.
Tests are made in a water tank, using models of propellers having the data as shown in the following table 1. The water tank is of a circular stream type and has an observational part of scales 5.0 m (length) X 2.0 m (width) X
1.0 m (depth). The maximum flow rate is 2.0 m/sec and the uniformity of the flow rate is within 1.5~.
Table 1 Type CP24 CP26 Diameter (mm) 220.0 220.0 Pitch ratio 0.8 1.2 ~2~9821 Developed ~lade area ratio 0.55 0.55 Boss ratio 0.18 0.18 Blade thikness ratio 0.05 0.05 Blade cross section shape MAU MAU
Blade number 4 4 In Fig. 4, a side view of a propeller characteristics measurement apparatus is shown partly by a section. This apparatus is located in the observational part of said water tank by securing its propeller open boat 41 to a rigid carrier (not shown) placed above the water tank. The boat 41 has a drive mechanism 43 to rotate a propeller 42 which may detachably be attached to its tip end, a thrust detector 44 and a torque detector 45.
Although not shown in the Fig. 4, a propeller rotating speed i5 measured by a digital counter TM-225 (product of Ono Measurement Instruments company, Japan) and a flow rate by a combination of a JIS type Pitot tube and a differential pressure converter DLPU-0.02 (product of Toyo Boldwin company, Japan). The analogue signals of such thrust, torque and flow rate represented by the differential pressure, etc. are converted to digital signals through an A/D converter provided in a microprocessor located in a separate controller and processed into physical data which then are printed by a pinter or plotted by a plotter.
~' -; .
-~X~98~
A thrust coefficient (KT) and a torque coefficient(KQ) are measured under different advance coefficients (J) adjusted by changing the flow rate while keeping the propeller rotating speed approprimately constant within the range of 7.5-9.0 r.p.s.. The depth in water of the propeller center is 300 mm and the direction of water flow is as shown by an arrow in the Fig. 4.
As a boss cap to be mounted on the propeller models, a cap of a rounded conical shape having a base diameter of 35 mm and a height of 25.6 mm is prepared. The cap may be mounted on the propeller by any known means and in these experiments a bolt-nut securing is employed.
As fins to be provided on the boss cap, those having six different triangular shapes (A)-~F) shown by a plan view in Fig. 5 are prepared from flat plates of l mm thickness to have the dimensions as shown in the following table 2.
Table 2 Fin shape Width Height (X-axis direction) (Y-axis direction) . _ _ _ . .
(A) 20 mm 20 mm (B) 26 mm 16.5 mm 1~9~1 (C) 26 mm 21 mm (D) 26 mm 28.5 mm (E) 26 mm 34 mm (F) 26 mm 39.5 mm Fig. 6 shows the relative positions of the fins and the boss cap. In this Eig. 6, a rear end O of a root 62 of a propeller blade 61 is set on the propeller axis 63 as a reference point. In this specification, a peripheral distance from the front end of a fin 64 to the plane including the reference point O and the propeller axis 63 is called "a" (positive in the direction of propeller rotation shown by an arrow). A surface distance from the front end of the fin 64 to a periphery including the reference point O
is called "b". The angle of the fin 64 against plane normal to the propeller axis is called "Alpha". The geometric pitch angle of the propeller blade root 62 is called "Epsilon".
In this specification, the geometric pitch angle "Epsilon" of a propeller blade root is one based upon a nose-tail line of the propeller blade root. More precisely, two surfaces of a cylindrical surface having an axis on the propeller axis and a radius equal to the boss radius and a propeller blade surface or its extension as a suspected surface are considered. A cylindrical surface intercepted , . . ' , ~X~
by a crossing line between these two surfaces, that is, a cylindrical section, is developed on a plane. In the developed vlew, an angle between a nose-tail line of the blade section defined by the developed cylindrical section and a line normal to a generatrix of the cylindrical surface corresponds to the "Epsilon".
The fin 64 is mounted on the boss cap in the direction perpendicular to the sheet of the Fig. 6, when no rake angle is given. The mounting is made, in these experiments, by cutting a groove on the boss cap, inserting the lower portion of the fin into the groove and fixing by means of an adhesive, but it is of course possible and in actual cases it is preferred to form the boss cap and the fins integrally as one body. The broken lines shown in the lower portions of fins in the Fig. 5 indicate crossing lines between the fin surface and the boss cap surface after mounting of the former on the latter.
Experiment 1 Water tank tests have been made by using the propeller of the type CP26 (Epsilon=67.4) and the fins of Fig. 5(C). The fins of total number 4, one for each ::
. ' :
12~9~21 propeller blade, are mounted on the boss cap in positions of a=lO mm, b=5 mm and Alpha=66. In this instance, the maximum diameter of the fins, that is, a doubled distance (2r) between the radially remotest end of a fin (from the propeller axis) and the propeller axis (after mounting of the fins on the boss cap) and a propeller diameter (2R) stand in a ratio r/R=0.23. Fig. l shows a front view of thus composed propeller l, boss 2, propeller blades 3, shaft 4, boss cap 5 and fins 6; and Fig. 2 shows a side view thereof. For comparison, tests have been made also as to cases without fins. The thrust coefficient (KT) and the torque coefficient (KQ) have been measured under various advance coefficients (J) of 0.0-l.l and the propeller efficiency (Eta= J KT/2PiKQ) has been calculated. Then an increase ratio (dEta) of the propeller efficiency increased from the cases without fins to the cases with fins has been calculated by percents. The results are shown in the following tables 3 and 4.
'; ' ~ ' ~ ' , 1~9~
Table 3 ( cases without f ins ) No . J KT KQ x 10 Eta _ 0 0.000 0.4816 0.9376 0.0000 1 0.050 0.4715 0.9092 0.0413 2 0.100 0.4606 0.8823 0.0831 3 0.150 0.4489 0.8565 0.1251 4 0.200 0.4363 0.8316 0.1670 0.250 0.4230 0.8071 0.2085 6 0.300 0.4088 0.7829 0.2493 7 0.350 0.3940 0.7586 0.2893 8 0.400 0.3785 0.7342 0.3282 9 0.450 0.3623 0.7094 0.3657 0.500 0.3454 0.6839 0.4019 11 0.550 0.3281 0.6578 0.4365 12 0.600 0.3102 0.6309 0.4695 13 0.650 0.2919 0.6031 0.5007 14 0.700 0.2731 0.5743 0.5299 0.750 0.2541 0.54450.5571 16 0.800 0.2349 0.51380.5820 17 0.850 0.2154 0.48200.6046 18 0.900 0.1959 0.44940.6244 19 0.950 0.1764 0.41590.6413 1.000 0.1570 0.38170.6547 21 1.050 0.1378 0.34680.6639 22 1.100 0.1189 0.31150.6680 :, ': ' .
12~
Table 4 ( cases with ~ins ) .
No . J KT RQ x 10 Eta dEta ( % ) . _ . .
00.000 0.4985 0.9154 0.0000 10.050 0.4894 0.8914 0.0437 5.55 20.100 0.4785 0.8677 0.0878 5.35 30.150 0.4660 0.8440 0.1318 5.09 40.200 0.4522 0.8204 0.1755 4.81 50.250 0.4373 0.7965 0.2184 4.54 60.300 0.4215 0.7724 0.2605 4.29 70 350 0.4050 0.7479 ~.3016 4.09 80.400 0.3880 0.7~29 0.3417 3.96 90.450 0.3705 0.6973 0.3806 3.90 100.500 0.3528 0.6710 0.4184 3.95 110.550 0.3349 0.6441 0.4552 4.09 120.600 0.3168 0.6164 0.4909 4.35 130.650 0.2986 0.5879 0.5255 4.73 14 0.700 0.2803 0.5585 0.5590 5.21 0.750 0.2617 0.5284 0.5913 5.78 16 0.800 0.2430 0.4974 0.6220 6.42 17 0.850 0.2239 0.4655 0.6506 7.07 18 0.900 0.2044 0 ~ 4328 0.6762 7.66 19 0.950 0.1843 0.3994 0.6976 8.07 1.000 0.1634 0.3652 0.71~3 8.09 21 1.050 0.1417 0.3303 0.7168 7.38 22 1.100 0.1187 0.2947 0.7053 5.29 , '~`~,' '' :
' ' ' ,: .' . -Fig. 7 illustrates the results of the tables 3 and 4 showing the advance coefficient (J) in abscissa and the thrust coefficient (KT), the torque coefficient multiplied by ten (KQ x 10) and the propeller efficiency (Eta) in ordinate. In this Fig. 7, curves T2, Q2 and P2 represents KT, KQ x 10 and Eta in the table 3 and curves T3, Q3 and P3 represents KT, KQ x 10 and Eta in the table 4. From this Fig. 7 and the table 4, it is understood that the propeller efficiency increases about 4-8% in the overall range of J=0.05-1.10 and particularly 7.66% at the usually employed J=0.9.
Further, in these tests, a needle pipe is manually put into the water from above the water tank to the close proximity of the rear end of the boss cap to supply air bubbles. It has been found that in the cases without fins, a large number of air bubbles align along the propeller axis, but in the cases with fins, air bubbles are diffused to disappear. It is considered that a hub vortex is greatly reduced by the merit of the fins.
Experiment 2 Tests similar to those shown in the Experiment 1 have been made, but using different positions of fins, that is, different a, b and Alpha. The propeller efficiency ' . ~ . .
.
'"
~2~9~21 increase ratio obtained under the usually employed advance coefficient (J)=0.9 is shown in the following table 5.
Table 5 No. a b Alpha Alpha- r/R dEta (mm) (mm)(~) Epsilon() (~) .. , . . . -- -- :
1 10 0 64 -3.4 0.25 5.49 2 15 0 61 -6.4 0.25 7.32 3* 10 5 66 -1.4 0.23 7.66 4 14 5 59 -8.4 0.23 6.39 * . . . from the data in the Experiment 1 The relative positions of fins and the propeller blade roots are illustrated in Fig. 8, wherein the rear end O of one propeller blade root shown in the Fig. 6 is placed on the base line X, and the blade position is shown as a line segment starting from the base line X with an angle Epsilon and ha~ing a length corresponding to the length of the nose-tail line of the propeller blade root. Another propeller blade root adjacent to said one also is shown is a similar manner, but at a peripheral distance between the rear ends of them taken in the direction of the base line X.
The positions of the fins are shown by taking "a" of the Fig. 6 in the direction of the base line X and "b" of the . ~ i , . : . . -- .
.
- - : - ' ' : -.
-Fig. 6 in the direction of a base line Y which passesthrough the reference point O normally to the base line X.
The lengths of the fin segments correspond to the lengths of the crossing lines between the fins and the boss cap as shown in the Fig. 5 by broken lines. From the table 5 and the Fig. 8, it is understood that a considerable improvement of propeller efficiency can be obtained when the front ends of fins are placed between the adjacent propeller blade roots, that is, within a space between extended nose-tail lines of the adjacent propeller blade roots.
Experiment 3 Tests similar to those of Experiment 1 have been made, but changing on]y Alpha. The propeller efficiency increase ratio obtained at the advance coefficient (J)=0.9 is shown in the following table 6.
Table 6 No. Alpha~) Alpha-Epsilon() r/R dEta(%) 1 45 -22.4 0.24 0.34 2 S0 -17.4 0.235 3.46 3* 66 - 1.4 0.23 7.66 4 85 17.6 0.22 3.80 S 90 22.6 O.Z2 2.19 , - . - : ' :
: ~ ' '' ' ' .
' ., ~ ' - ~
~9~
- 18 - , 6 95 27.6 0.22 2.38 7 100 32.6 0.22 0.77 8 105 37.6 0.22 0.47 * . ~ . from the data of Experiment 1 The results of the table 6 are shown in Fig. 9 similarly to the Experiment 2. It is understood from the table 6 and the Fig. 9 that a considerable improvement of propeller efficiency can be obtained within the range of -20 c Alpha-Epsilon ~30 -Experiment 4 Tests similar to those of Experiment 2 have beenmade, but using the propeller of the type CP24 (Epsilon=57.4~) and the fins of the Fig. 5(A) and 5(C). The propeller efficiency increase ratio obtained at the advance coefficient (J)=0.6 usually employed for such propeller is shown in the following table 7.
Table 7 No. a b Alpha Alpha- r/R Fin shape dEta (mm) (mm) () Epsilon(~) (%) .. _ . _ . _ _ .
1 0 5 80 22.6 0.21 (A) 2.03 '''~
.. .. .
. . .
.. . . . .
' ' -' : . . ' .,:, ~ .:' ' , .- - . ~ i 2 10 17 63 5.6 0.18 (A) 3.02 3 5 12 63 5.6 0.20 (A) 2.06 4 5 9.5 63 5.6 0.21 (A) 2.32 7 63 5.6 0.215 (A) 2.84 6 10 7 63 5.6 0.23 (C) 3.93 7 10 7 57 -0.4 0.22 (C) 2.32 8 6 7 63 5.6 0.22 (C) 2.57 9 4 5 35-22.4 0.235 (C) -0.09 10 4 5 9032.6 0.22 (C) -O.lg The results of the table 7 are shown in Fig. 10 similarly to Experiment 2. It is understood that there is no material difference between the fin shapes (A) and (C) and that the fin positions should satisfy the conditions that the front end of the fin is located between the adjacent propeller blade roots and the inclination of the fin stands within the range of -20~Alpha-Epsilon S 30 , as in the case of said Fig. 9.
Ex ~
The test of Experiment 4, No. 6 has been repeated, adding rake angles of +30 to the fins~ The rake angles are measured from the direction perpendicular to the sheet of the Fig. 6 to the direction of rotation of the propeller.
The results are shown in the following table 8.
' ' ~ .
; , .
1~9~2~.
Table 8 No. a b Alpha Alpha- r/R Rake Angle dEta (mm) (mm) () Epsilon() () (~) 6F 10 7 63 5.6 0.21+30 1.46 6M* 10 7 63 5.6 0.23 0 3.93 6B 10 7 63 5.6 0.21-30 4.47 * . . . from the data of Experiment 4 From the table 8, it is understood that there is a tendency of further improvement of dEta when a rake angle opposite to the rotation direction of the propeller is added to fins. The mounting positions of fins are shown in Fig. 11 by way of a side view similar to the Fig. 6 and in Fig. 12 which is an A-A line section of the Fig. 11.
Experiment 6 The tests of Experiment 4, No. 7 has been repeated, but by changing the number and positions of the fins. the results are shown in the following table 9.
'~
' ' ' ~ ~ ',~ ',; ' ' ', : . . ~ - , -' . ', ~
: . , 12~
- Table 9 No.a b Alpha Alpha- r/R FindEta (mm) (mm) (o) Epsilon() Number (%?
7~N210** 7 57 -0.4 0.22 2-0.12 7-N310** 7 57 -0.4 0.22 30.49 7-N4* 10 7 57 -0.4 0.22 42.32 7-NS10** 7 57 -0.4 0.22 5-1.12 * . . . from the data of Experiment 4 ** . . . value of one specific fin; values of the other fins correspond to the positions determined by the quotient of 360 . divided by the number of f ins The relative positions of the propeller blade roots and the fins are shown in Fig. 13 by way of X-Y plane as in the Figs. 8-10. Relative to the four propeller blade roots Bl-B4, the fins are located, in the case of fin number two, at the positions l/F and 2/2; in the case of fin number three, at the positions l/F, 2/3 and 3/3; in the case of fin :. number four, at the positions l/F, 2/4, 3/4 and 4/4; and in : the case of fin number five, at the positions l/F, 2/5, 3/5, 4/5 and 5/5, as shown in the Fig. 13. It can be seen therefrom that there is no fin located, in the case of fin number two, between the propeller blade roots B2 and B3 and ;l .
-.
' 9~
between B4 anu Bl; in the case of fin number three, between s3 and s4. Further, there are two fins between B3 and B4 in the case of fin number five. Thus the fins are not evenly positioned in the cases of fin number two, three and five.
It is understood from the table 8 that the number of fins should be same for each space between the adjacent propeller blade roots.
Experiment 7 .
Tests similar to those of Experiment 1 have been made, but by using various fins of the Fig. 5(B)-5(F) having the same width but different heights. Total four same shape ; fins, one for each propeller blade, are mounted in the positions determined by a=10 mm, b=5 mm and Alpha=66. The propeller efficiency increase ratio obtained at the advance coefficient (J)=0.9 is shown in the following table 10.
Table 10 No. a b Alpha Alpha- r/R Fin shape dEta (mm) (mm) () Epsilont) (~) 1 10 5 66 -1.4 0.2 (B) 4.12 2* 10 5 66 -1.4 0.23 (C) 7.66 3 10 5 66 -1.4 0.3 (D) 6.08 ,:`,.`,`
.
., ' ': ' .: ~- - , 4 10 S 66 -1.4 0.35 (E) 0.87 5 66 ~1.4 0.4 (F) -0 50 * . . . from the data of Experiment 1 The results of the table 10 are illustrated in Fig. 14, taking r/R in abscissa and dEta in ordinate.
In view of the fact that the boss ratio of the propeller of type CP26 is 0.18, it is unerstood that the maximum diameter of the fins should be greater than the diameter of the cap-mounting end of the boss and not be greater than 33% of the propeller diameter, in order to obtain a considerable improvement of the propeller efficiency.
Experiment 8 Tests similar to those of Experiment 1 have been made, but by using fins of the Fig. 5(C) bended to an arc of radius 50 mm. Two kinds of fins, one bended to the arc convex in the direction of propeller rotation (= C-out) and the other to the arc concave in the direction of propeller rotation (= C-in), are used. Total four same shape fins, one for each propeller blade, are mounted in the positions dete_mined by a=10 mm, b=5 mm and Alpha=66~ (= angle of the ', ':
- ; : .
' ,- ' : . - ' .:
. , ~ .
~z~
direction of the chord of the arc). The propeller efficiency increase ratio as obtained at the advance coefficient (J)=0.9 is shown in the following table 11.
Table 11 No. a b Alpha Alpha- r/R Fin shape dEta (mm) (mm) () Epsilon() (%) _ 1 10 5 66 -1.4 0.23 C-out 6.46 2* 10 5 56 -1.4 0.23 C 7.66 3 10 5 66 -1.4 0.23 C-in 6.94 * . . . from the data of Experiment 1 From the above data, it is understood that the shape of fins is not limited to plane and may have a positive or a negative camber.
As explained in detail above, it is possible to improve the propeller characteristics particularly the propeller efficiency without increasing torque, by the effect of guiding the water stream rearward of the boss cap to a direction of reducing generation of hub vortex, through the provision of fins on a boss cap to be mounted on a screw propeller in accordance with the present invention.
, ' " ' ' ' ' ' . ' , ' ', ' ' , ~ , '' . ~ ' ' . ~ ' ' '" . . , ' ' ' . :
' . . .
.
' , ' .
According to such invention, further merits are obtained, for example, the propeller characteristics may greatly be improved only by a slight modification of a rather small boss cap and not by a drastic change of the screw propeller itself, to which the boss cap is appended, necessitating difficult work and high cost. In effect, the present invention is applicable to screw propellers already mounted on existing ships, simply by exchanging or working the boss cap without incurring high cost.
~ , .. ~ -, . , -.
- . .
., ' : ' ' :
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination:
a screw propeller having a hub and a plurality of propeller blades thereon each having a leading edge toward a front of the propeller and a trailing edge toward the rear of the propeller and a root along a root line on the hub extending from the leading edge to the trailing edge, said roots lying along a line at a pitch angle to a plane perpendicular to the axis of rotation of said propeller; and a cap body having a front cap mounting end mounted on said hub at the rear of said propeller, and a rear end, a plurality of fins mounted on said cap body at intervals spaced around the periphery of said cap body, (i) the number of fins being the same as the number of propeller blades and respectively corresponding to the propeller blades, (ii) said fins being inclined at an angle to the line along which the root of the corresponding propeller blade lies, which angle is from -20° to +30° relative to the rotational direction of the screw propeller and is selected to receive a stream from the propeller blades at a side facing toward the propeller blades, and being inclined at a rake angle RA which is -30°< RA < 0° relative to the direction of rotation of said screw propeller, and said fins having leading edges which are toward said propeller and which are behind the rear end of the roots of said propeller blades and between lines starting respectively from the leading and trailing edges of the roots of the propeller blades and extending rearwardly in parallel to the axis of rotation of said propeller, said fins being substantially smaller in blade area than the propeller blades and having roots along said cap body, the ends of the roots of trailing edges of said fins spaced in the circumferential direction of said cap body and being spaced toward said propeller from the rear end of said cap body; and (iii) the outer diametric dimension of said fins from the axis of said cap being larger than the diameter of said cap body at the rear of said propeller hub and no larger than 33% of the outer diametric dimension of said screw propeller as measured from the axis of rotation of the screw propeller.
a screw propeller having a hub and a plurality of propeller blades thereon each having a leading edge toward a front of the propeller and a trailing edge toward the rear of the propeller and a root along a root line on the hub extending from the leading edge to the trailing edge, said roots lying along a line at a pitch angle to a plane perpendicular to the axis of rotation of said propeller; and a cap body having a front cap mounting end mounted on said hub at the rear of said propeller, and a rear end, a plurality of fins mounted on said cap body at intervals spaced around the periphery of said cap body, (i) the number of fins being the same as the number of propeller blades and respectively corresponding to the propeller blades, (ii) said fins being inclined at an angle to the line along which the root of the corresponding propeller blade lies, which angle is from -20° to +30° relative to the rotational direction of the screw propeller and is selected to receive a stream from the propeller blades at a side facing toward the propeller blades, and being inclined at a rake angle RA which is -30°< RA < 0° relative to the direction of rotation of said screw propeller, and said fins having leading edges which are toward said propeller and which are behind the rear end of the roots of said propeller blades and between lines starting respectively from the leading and trailing edges of the roots of the propeller blades and extending rearwardly in parallel to the axis of rotation of said propeller, said fins being substantially smaller in blade area than the propeller blades and having roots along said cap body, the ends of the roots of trailing edges of said fins spaced in the circumferential direction of said cap body and being spaced toward said propeller from the rear end of said cap body; and (iii) the outer diametric dimension of said fins from the axis of said cap being larger than the diameter of said cap body at the rear of said propeller hub and no larger than 33% of the outer diametric dimension of said screw propeller as measured from the axis of rotation of the screw propeller.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP181,577/86 | 1986-07-31 | ||
| JP18157786 | 1986-07-31 | ||
| JP188,898/86 | 1986-08-11 | ||
| JP18889886 | 1986-08-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1289821C true CA1289821C (en) | 1991-10-01 |
Family
ID=26500707
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 543348 Expired - Lifetime CA1289821C (en) | 1986-07-31 | 1987-07-30 | Screw propeller boss cap with fins |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0255136A1 (en) |
| AU (1) | AU593670B2 (en) |
| CA (1) | CA1289821C (en) |
| FR (1) | FR2619352A1 (en) |
| GB (1) | GB2194295B (en) |
| HK (1) | HK85092A (en) |
| SG (1) | SG60592G (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11713101B2 (en) | 2020-12-04 | 2023-08-01 | Jeffrey L. HATHAWAY | Propeller hubcap |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU593670B2 (en) * | 1986-07-31 | 1990-02-15 | Mikado Propeller Co., Ltd. | A screw propeller boss cap with fins |
| JP2947357B2 (en) * | 1989-08-18 | 1999-09-13 | 日産自動車株式会社 | Propeller structure of high-speed boat |
| US5096383A (en) * | 1989-11-02 | 1992-03-17 | Deutsche Forschungsanstalt Fur Luft- Und Raumfahrt E.V. | Propeller blades |
| EP0758606A1 (en) * | 1995-08-16 | 1997-02-19 | Schottel-Werft Josef Becker GmbH & Co KG. | Hub cap for ship propellers |
| DE10152977C1 (en) * | 2001-10-26 | 2003-05-08 | Howaldtswerke Deutsche Werft | Device for counteracting flow vortices generated in the hub area of propellers and / or propeller drives in the surrounding fluid |
| FI115210B (en) | 2002-12-20 | 2005-03-31 | Abb Oy | Device in a propulsion system |
| RU2584038C2 (en) * | 2010-07-12 | 2016-05-20 | Роллс-Ройс Актиеболаг | Sea vessel to operate in ice conditions |
| DE102011055515A1 (en) | 2011-11-18 | 2013-05-23 | Becker Marine Systems Gmbh & Co. Kg | Propeller arrangement, in particular for watercraft |
| CN103115021B (en) * | 2013-02-01 | 2015-03-04 | 华中科技大学 | Vane wheel device |
| EP3150482B1 (en) * | 2014-05-28 | 2020-07-01 | Korea Institute of Ocean Science and Technology | Combined propeller cap for reducing rotating flow and hub vortex and enhancing propulsion efficiency |
| JP6812057B2 (en) * | 2017-06-21 | 2021-01-13 | ナカシマプロペラ株式会社 | Propulsion device for ships and ships equipped with it |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE606119C (en) * | 1933-11-12 | 1934-11-24 | Nicholas Wladimir Akimoff | Device to increase the efficiency of a screw propeller |
| GB652441A (en) * | 1948-05-19 | 1951-04-25 | Edward Shellberg | Air deflectors for airplane propellers |
| US2755868A (en) * | 1953-09-17 | 1956-07-24 | United Aircraft Corp | Spinner construction for an aeronautical propeller |
| GB752765A (en) * | 1953-09-17 | 1956-07-11 | United Aircraft Corp | Improvements in or relating to a spinner construction for an aeronautical propeller |
| US3606579A (en) * | 1969-01-22 | 1971-09-20 | Henry Mehus | Propeller |
| BE789482A (en) * | 1971-10-04 | 1973-01-15 | Gen Electric | CONSTRUCTION OF DE-ICING WHEEL FOR TURBOMACHINE |
| DE3037369A1 (en) * | 1980-09-01 | 1982-03-11 | Escher Wyss Gmbh, 7980 Ravensburg | Low drive marine screw - has set of vanes around rear end of hub smoothing water flow |
| AU593670B2 (en) * | 1986-07-31 | 1990-02-15 | Mikado Propeller Co., Ltd. | A screw propeller boss cap with fins |
-
1987
- 1987-07-30 AU AU76301/87A patent/AU593670B2/en not_active Expired
- 1987-07-30 EP EP87111052A patent/EP0255136A1/en not_active Withdrawn
- 1987-07-30 CA CA 543348 patent/CA1289821C/en not_active Expired - Lifetime
- 1987-07-31 GB GB8718165A patent/GB2194295B/en not_active Expired - Lifetime
- 1987-08-12 FR FR8711462A patent/FR2619352A1/en not_active Withdrawn
-
1992
- 1992-06-08 SG SG60592A patent/SG60592G/en unknown
- 1992-11-05 HK HK85092A patent/HK85092A/en not_active IP Right Cessation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11713101B2 (en) | 2020-12-04 | 2023-08-01 | Jeffrey L. HATHAWAY | Propeller hubcap |
Also Published As
| Publication number | Publication date |
|---|---|
| HK85092A (en) | 1992-11-13 |
| GB2194295A (en) | 1988-03-02 |
| AU7630187A (en) | 1988-02-04 |
| FR2619352A1 (en) | 1989-02-17 |
| SG60592G (en) | 1992-09-04 |
| EP0255136A1 (en) | 1988-02-03 |
| GB8718165D0 (en) | 1987-09-09 |
| GB2194295B (en) | 1991-03-20 |
| AU593670B2 (en) | 1990-02-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1289821C (en) | Screw propeller boss cap with fins | |
| US4073601A (en) | Marine propeller | |
| AU766263B2 (en) | A single or multi-bladed rotor | |
| BR8004833A (en) | MARITIME PROPULSOR | |
| US4427341A (en) | Side propellers for the propulsion of fast boats and aircraft | |
| CA1231274A (en) | Ring propeller | |
| US10040528B2 (en) | Propulsion device for ship | |
| GB2066371A (en) | Marine propeller | |
| JPS63154494A (en) | Propeller boss cap provided with fin | |
| US6106232A (en) | Propeller structure | |
| US4137709A (en) | Turbomachinery and method of operation | |
| US4921404A (en) | Propellors for watercraft | |
| US4218190A (en) | Flat-bladed fan wheel of diagonal-flow fan | |
| KR970000169B1 (en) | Boss cap with fins of a screw propeller | |
| US20230193761A1 (en) | Propeller | |
| GB2027132A (en) | Propeller | |
| US4530644A (en) | Device for deriving energy from a flowing medium | |
| FI90029C (en) | PROPELLERNAV | |
| JPH0786358B2 (en) | fan | |
| CA1229765A (en) | Fluid contacting surfaces and devices incorporating such surfaces | |
| DK169282B1 (en) | Screw propeller boss with fins - has fins equal in number to blades of propeller, mounted so that their leading edges fall between blade roots | |
| NO167560B (en) | Hub cap for a screwdriver. | |
| WO1990013746A1 (en) | Propeller | |
| CN219821727U (en) | Propeller flow guide cap with high propulsion efficiency | |
| CN212243767U (en) | Conduit type high-efficiency propeller |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |